Why is it better to ask for forgiveness than permission?

Like all such quotations which are taken out of their natural context (and even their wording is altered), it all depends on many factors. For instance, whether or not the choice comes down to only these two options, whether there is a prominent hierarchy of power at play, is the cost of being a maverick among the conformists majority a justified one, etc.

But if a person has their ego and individualism in check and trust their instinct to be in benefit of their larger group and their goal, then sure it is justified to proceed now and ask for forgiveness later.

this is military headset-

-doing something even if it turns out to be a wrong choice is superior to doing nothing. when you do nothing you froze in the face of demand.

thus for lack of supervision, do something other than stand around wondering if its ok to do something.